Add BLE HID Host app; share the central layer via libble/

Extract the reusable BLE central/GATT client and name/value decoders into
libble/ (moved out of bt_inspector). build.sh now stages libble/*.{c,h}
into each app dir at build time and builds every app in APPS=(...).

New app ble_hid_host: connects to a BLE keyboard or mouse, discovers the
HID service (0x1812), sets protocol mode (boot when offered, else report),
subscribes to the input-report characteristics, and decodes keyboard
(modifiers + key names) and mouse (buttons + dx/dy/wheel) reports live.
Events scroll on screen and are logged with raw bytes to
apps_data/ble_hid_host/. No pairing, so encryption-gated keyboards stay
silent; open devices and most mice work. Both faps build and pass APPCHK.

ble_hid_host/application.fam

@@ -0,0 +1,16 @@
+# External app. Needs firmware built by ../build.sh: full BLE stack plus the
+# ST aci_*/hci_* command API exported to apps.
+App(
+    appid="ble_hid_host",
+    name="BLE HID Host",
+    apptype=FlipperAppType.EXTERNAL,
+    entry_point="ble_hid_host_app",
+    requires=["gui", "storage"],
+    stack_size=4 * 1024,
+    fap_category="Bluetooth",
+    fap_icon="icon.png",
+    fap_version="1.0",
+    fap_description="Connect a BLE keyboard or mouse and watch its input reports",
+    fap_author="andydixon",
+    fap_weburl="https://github.com/andydixon/flipper-bt-inspector",
+)